This invention relates to inductive write heads, and particularly to thin film inductive write heads having a two-piece pole.
Inductive write heads are formed by a pair of magnetic poles that are joined at a back region, and separated by a small insulation layer forming a front or transducing gap at the air bearing surface (ABS). Coils embedded in the insulation material between the poles permit writing of data to a recording surface adjacent the ABS. Current flowing through the coils induces a magnetic flux in the poles, generating a magnetic field adjacent the gap at the ABS which induces the recording of data on the adjacent moving magnetic media. Currently, inmost read heads are magniietoresistive heads, not inductive heads, as inductive head technology is almost exclusively directed lo write heads. Accordingly, although the invention will be described in connection with a write head, it is understood that the invention is equally applicable to inductive read heads.
There is a continuing need in the data recording art to increase the data density, and hence the capacity of magnetic discs of magnetic disc drives. Data density is increased by making the concentric tracks more narrow, thereby increasing the number of tracks per radial inch, and by decreasing the length of the bit cell along the track, thereby increasing the number of bit cells per track. Both track width and bit cell length are factors of the geometry of the write head, and its ability to write data to the track. More particularly, the track width is largely dictated by the width of the wrilt the length of a bit cell is largely dictated by the length the write gap and the coil current switching interval. By coil,ciltioii, gap width is defined as the width of the gap across the head in the general direction of the radial width of the track. Gap length is defined as the length between opposing poles of the head, generally along the length of the track. Gap height is the direction orthogonal to both the length and width of the gap, and is a distance from the ABS into the head. Commonly, the height of a gap is called the throat height which is the distance between the ABS and a "zero throat position" where both of the two pole layers converge at the transducing gap. If one pole converges to the gap level at a location different from the other pole, the zero throat position is the location at the convergence of the pole closest to the ABS. Typically, the zero throat position is 1 or 2 .mu.m from the ABS.
Narrow track widths are achieved by use of narrow poles at the gap of the write head. However, the pole width must be large in the paddle region of the head where the coil passes between the poles. The larger pole width is necessary to gain adequate magnetic flux through the poles by the coil write current. Hence, it is common to taper the poles from a large width in the paddle region to a narrow width at the ABS. To achieve even narrower widths, two-piece poles have been introduced that employ a first pole piece having a very narrow width at the ABS, and a second pole piece connected to the first pole piece and extending to the back region of the head. Thus, the first pole piece defines the narrow track width, and the second pole piece links through the coils and connects to the other (e.g., bottom) pole. An example of a two-piece pole may be found in U.S. Pat. No. 5,452,164 issued to Cole et al.
The second pole piece of a two-piece pole is wider at the ABS that the first pole piece. As a result, sharp corners are formed in the second pole piece at the ABS. These sharp corners produce large fringe magnetic fields during the write process, thereby adversely affecting the quality of the recording of data. More particularly, the fringe field may adversely affect data recorded on adjacent tracks by re-writing magnetic transitions.